Secondhand smoke is a mixture of mainstream smoke and side stream smoke. Mainstream smoke is the smoke inhaled or exhaled by the smoker where as the side stream smoke is the smoke given off by burning end of tobacco products. Secondhand smoke consists of carcinogens and poisons.

Secondhand smoke has more than 4000 chemical compounds. It has been estimated that about 200 of those are poisonous and 60 are carcinogens. Some of the chemical compounds that secondhand smoke contains are formaldehyde, cyanide, carbon monoxide, ammonia and nicotine. Most of those chemicals are well known carcinogens.

Secondhand smoke has some adverse affects on children including severe asthma, acute respiratory infections, sudden infant death syndrome, and ear problems. Since the breathing rate of children is fast, their lungs receive a higher amount of toxins when air tainted with cigarette smoke is inhaled. The risks a child faces due to secondhand smoke include lower birth weight, bronchitis, pneumonia, asthma, dental decay and nose and eye irritation. In addition children can develop increased risk for developmental issues such as learning disabilities. The most severe risk that can develop in infants is Sudden Infant Death Syndrome (SIDS). This can develop in babies whose mothers smoked during pregnancy. SIDS can develop when the chemicals in cigarette smoke are transferred to a fetus through the placenta. A study shows that annually, about 1900 to 2700 children develop difficulties due to exposure to secondhand smoke.

Lung cancer is the most common form of cancer caused by secondhand smoke. Secondhand smoke has been classified as a Group A carcinogen by The Environment Protection Agency. Cancers caused by secondhand smoke include the following types of cancer: lung cancer, breast cancer, nasal sinus cavity cancer, bladder cancer and cervical cancer. Secondhand smoke contains chemical compounds, which become carcinogens only after they come in to contact with certain enzymes present in the tissues of the human body.

Nicotine in tobacco is absorbed when someone is exposed to secondhand smoke. Nicotine, through the discharge of epinephrine from the adrenal cortex, provides an “immediate kick”. This causes a sudden release of glucose as a result of stimulation by the endocrine glands and central nervous system. Soon after that, fatigue and depression will lead the user to seek more nicotine. Research had shown that nicotine contained in tobacco, marijuana, heroin, and cocaine affect the pathways of brain that control pleasure and reward.

When a passive smoker is exposed to tobacco by secondhand smoke, nicotine is absorbed by the lungs and passed into the blood stream where it is circulated to the brain. This happens within 8 seconds after the inhalation of tobacco smoke. Nicotine can also enter the body through mucous membranes. The adverse affect of nicotine is how it can change heart rate, blood pressure, and breathing pattern due to the changes it creates in the nerves.

The brain is made of billions of nerve cells that communicate by releasing neurotransmitters, or chemical messengers. Each neurotransmitter fits to a receptor and activates a receptor’s nerve cell. The molecule of nicotine is shaped like a neurotransmitter called acetylcholine. The acetylcholine and its receptors stimulate functions like learning, memory, breathing, and muscle movement. The nicotine attaches to the acetylcholine receptors, upon reaching the brain and mimics the action of acetylcholine.

Being exposed to secondhand smoke has many risk factors. Being exposed to secondhand smoke can lead to increased risk of developing lung cancer by 20 to 30 percent and heart disease by 25 to 30 percent. Non-smokers also affected by respiratory problems that include increased phlegm production, coughing and reduced lung function.

A report suggests that tobacco use (second hand smoke contains tobacco) is the most avoidable cause of disability; disease and death in US. Secondhand smoke increases the risk of developing lung cancer, in addition to the adverse effects it can cause to the heart. It is estimated that 35000 to 62000 deaths are due to heart disease in non-smokers who are exposed to secondhand smoke. Continual exposure to second hand smoke can lead to adverse effects on the heart such as narrowing of carotid arteries (arteries which carry blood to brain) and atherosclerosis (hardening of the arteries).